Background: Pertussis outbreaks are occurring throughout North America. To assess the utility of physician diagnosis in estimating vaccine effectiveness, we sought to validate physician diagnosis of Bordetella pertussis (BP) against laboratory confirmed cases. Alberta has a universal publicly funded health care insurance system. The Alberta Ministry of Health (AH) captures the ICD-9 coded diagnoses for all physician billing records and hospitalizations. All lab positive and epidemiologically linked cases of notifiable diseases, includingBP, are also forwarded to public health within AH. All records include a Unique Lifetime Identifier (ULI) for the patient

Methods: We used PCR positive cases notified to public health as the gold standard (public health diagnosed). We extracted records with ICD-9 codes of 033, 033.0, 033.1, 033.8, and 033.9 from physician billing and hospitalization databases (physician diagnosed BP). Public health records were deterministically linked with billing and hospitalization data using ULIs. Numbers and proportions of true positive (TP: public health AND physician diagnosed), false positive (FP: only physician diagnosed) and false negative (FN: only public health diagnosed) cases were estimated. Sensitivity (SE) was calculated as TP/TP+FN; positive predictive value (PPV) as TP/TP+FP. Physician inaccuracy was calculated as FN/TP+FN. Analysis is ongoing as data are received for negative predictive value and specificity.